Portable electronic communication devices continue to integrate multiple functions beyond their core communications with great popularity, including for example still and/or video cameras, music storage and playing, GPS circuitry, and Internet operability. These desires of customers for multiple functionality lies in opposition to their desire for small size in the same communication device, so manufacturers increasingly seek to make components multi-functional and increase functionality via software to serve these competing customer desires while containing costs and size. One feature of enduring customer popularity is both an audible and a silent alert for incoming communications, common on devices such as mobile stations and pagers and selectable by a user. The silent alert is selected, for example, when the user desires to be made aware of an incoming call or page without interrupting all nearby participants in a meeting or social engagement. With few recent exceptions, the vibration mechanism has been dedicated solely to the silent alert function.
The vibration mechanism typically includes a (relatively) massive rotor mounted to a shaft that is driven by an electric motor activated by an incoming communication when the user selects the silent mode. The rotor is purposefully not rotationally balanced about the shaft, so rotation of the shaft causes a noticeable vibration. The eccentricity of the rotor's mass about the shaft is selected to be substantial enough to cause the entire mobile station or pager to vibrate, gaining the attention of a user holding the device in his/her hand or pocket. Typically, the electric “vibration” motor is mounted directly to the housing of the device.
Relevant teachings, by which the vibration mechanism may be used for the synthesis of low-frequency sound in addition to its traditional function of silent vibration alerts, is described in U.S. Pat. No. 6,809,635, issued on Oct. 26, 2004 and entitled “Mobile Terminal Using a Vibration Motor as a Loudspeaker and Method of Use Thereof”, which is hereby incorporated by reference. That incorporated patent also refers to U.S. Pat. Nos. 5,300,851; 5,373,207; 6,081,055; 5,783,899; 5,861,797 and 5,960,367, as well as European Patent Applications EP 0 688 125 A1; 1 001 249 A2 and 1 035 633 A1 as describing vibration motors and their implementations. These teachings are directed to increasing the functionality of such a vibration mechanism.